In order to successfully exploit subterranean hydrocarbon reserves, information about the subsurface formations and formation fluids intercepted by a wellbore is generally required. This information may be obtained via sampling formation fluids during various drilling and completion operations. The fluid may be collected and analyzed, for example, to ascertain the composition and producibility of hydrocarbon fluid reservoirs.
Downhole sampling tools commonly include a fluid entry port (or probe), one or more packers for isolating the fluid entry port from the remainder of the borehole, a fluid inlet valve, and one or more sampling chambers. Owing to the potential for obtaining contaminated samples, it is sometimes desirable to collect multiple samples using a single sampling tool. Sampling tools configured for obtaining multiple samples, commonly include a large number of inlet valves (and corresponding electronic control circuitry) connected to various fluid flow lines. While such tools may be serviceable, increased tool complexity can lead to reliability problems, especially in high temperature, high pressure wellbore environments.
Therefore there is a need in the art for improved formation fluid sampling tools, particularly for obtaining multiple fluid samples.